Scanning laser ophthalmoscopes are used to examine the ocular fundus and have the following advantages over known retina cameras for photometric measurements:
the asymmetric division of the aperture diaphragm in the eye pupil to the advantage of the measurement aperture; PA1 the high radiation intensity permissible for brief periods on a small examination location; PA1 the basic possibility of measuring in the direction of the optical axis (scanning laser tomography).
Scanning laser ophthalmoscopes carrying out point-by-point scanning of the ocular fundus are known, wherein a detector records the light reflected from every point on the ocular fundus. An image of the ocular fundus is formed after synchronous assignment of the image points to a line and, further, of the lines to an image. This image can be a reflection image or --when a blocking filter is incorporated --a fluorescence image. The image obtained in this way can be stored digitally after analog-to-digital conversion of the pixel signals and is then available for further image processing.
An ophthalmoscope of this kind is described, for example, in WO 88/03396 and DE 3638226 A1. In these cases, a plurality of individual detectors which are preferably arranged in the shape of a circle sector are provided for the acquisition and detection of the surface intensity distribution of the reflected light from different planes and its polarization state.
DE 3818084 A1 likewise describes an ocular fundus camera with laser beam scanning in which a reflection image is obtained simultaneous with the florescence image for focussing the image of the ocular fundus during fluorescein angiography.
EP 307185 A2 is directed to a scanning device with a detector array and with an anamorphotic element for generating a stripe-shaped focussed image which is guided over the retina.
DE 3037983 C2 is not related to raster-type detection of the ocular fundus. An embodiment example relates to scanning by means of a diode array which extends in the scanning direction as a receiver. Only the point on the sample or specimen that is being illuminated at the moment is imaged on an available receiver. The behavior of the fluorescent radiation with respect to time can be adjusted by selecting determined diode groups and a delay time between the illumination of the point on the specimen and the detection of fluorescent radiation. The diodes are read out synchronous with the scanning frequency. For the individual points on the specimen, the type of scanning gives various possibilities for detecting values at all. There is a conflict between the relationship to scanning speed and scanning frequency on the one hand and the desired acquisition of time processes such as fluorescence which last longer than the time period of a scanning step on the other hand. In the microscope described in CZ 4966 DE, the relationship to scanning frequency is abandoned, but the arrangement is then no longer suitable for normal scanning image generation.